The JLab 12 GeV Upgrade
Antje Bruell, JLab
PacSpin 2007, Vancouver, Canada
• Upgrade of accelerator and experimental equipment
• Highlights of the physics program @ 12 GeV
• Highlights of spin dependent measurements @ 12 GeV
• Timelines and schedule
Jefferson Lab Today
2000 member international user community
engaged in exploring quark-gluon structure of
matter
Superconducting
accelerator provides
100% duty factor
beams of
unprecedented
quality, with energies
up to 6 GeV
CEBAF’s innovative design
allows delivery of beam with unique properties
to three experimental halls simultaneously
Each of the three halls offers complementary
experimental capabilities and allows for large equipment
installations to extend scientific reach
A
B
C
Jefferson Lab Today
Hall B
Hall A
Two high-resolution
4 GeV spectrometers
Large acceptance spectrometer
electron/photon beams
Hall C
A
B
7 GeV spectrometer,
1.8 GeV spectrometer,
large installation experiments
C
116 GeV CEBAF
12
Upgrade magnets
and power
supplies
CHL-2
Enhanced capabilities
in existing Halls
Lower pass beam energies
still available
Experimental equipment for 12 GeV
Hall D – exploring origin of confinement by
studying exotic mesons
Hall B – understanding nucleon structure via
generalized parton distributions
Hall C – precision determination of valence quark
properties in nucleons and nuclei
Hall A – short range correlations, form factors,
hyper-nuclear physics, future new experiments
Technical Performance Requirements
Hall D
Hall B
Hall C
Hall A
excellent
hermeticity
luminosity
energy reach
installation
space
polarized photons
hermeticity
10 x 1034
precision
Eg~8.5-9 GeV
11 GeV beamline
108 photons/s
target flexibility
good momentum/angle resolution
excellent momentum resolution
high multiplicity reconstruction
luminosity up to 1038
particle ID
Physics Experimental Equipment
total project cost: $ 310 M
Physics TEC by Sub System
Hall A
1.2%
Experimental Systems
PED
3.1%
Construction
38.2%
Remainder of
12GeV Upgrade
TEC
58.8%
Hall B
33.3%
Hall D
38.8%
Hall C
26.8%
QCD and confinement
Small Distance
High Energy
Large Distance
Low Energy
Perturbative QCD
Strong QCD
High Energy Scattering
Gluon
Jets
Observed
Spectroscopy
Gluonic
Degrees of Freedom
Missing
GluonicExcitations
Excitations
Gluonic
• predicted by QCD
• crucial for understanding
confinement
• quantum numbers of the excited
gluonic fields couple to those of the
quarks to produce mesons with exotic
quantum numbers
• mass spectra calculated by lattice
QCD
possibility for experimental search
Flux
tube
forms
between
qq
From G. Bali
Hybrid mesons and mass predictions
q
Hybrid mesons
1 GeV mass difference
q
Normal mesons
q
q
Jpc = 1-+
Lattice
1-+ 1.9 GeV
2+- 2.1 GeV
0+- 2.3 GeV
Lowest mass expected to
be p1(1−+) at 1.9±0.2 GeV
GlueX / Hall D Detector
12 GeV electrons
Barrel Lead Glass
Calorimeter Detector
Solenoid
collimated
herent Bremsstrahlung
Photon Beam
Note that tagger is
80 m upstream of
detector
Electron Beam from CEBAF
Time of
Tracking Flight
Cerenkov
Counter
Target
Finding an Exotic Wave
An exotic wave (JPC = 1-+) was generated at level of 2.5 % with 7 other
waves. Events were smeared, accepted, passed to PWA fitter.
X(exotic )  p  3p
Mass
Input: 1600 MeV
Output: 1598 +/- 3 MeV
500
500
events/20 MeV
generated
400
400
PWA fit
300
300
Width
Input: 170 MeV
Output: 173 +/- 11 MeV
200
200
100
100
Statistics shown here correspond
to a few days of running.
Double-blind M. C. exercise
0
0
1.2
1.2
1.4
1.4
1.6
1.6
1.8
1.8
Mass (3 pions) (GeV)
Neutron/Proton Charge Form Factor @12 GeV
(Polarization Experiments only)
Here shown as ratio of Pauli & Dirac Form Factors F2 and F1,
ln2(Q2/L2)Q2F2/F1  constant when taking orbital angular momentum into account (Ji)
Charged Pion Electromagnetic Form Factor
Where does the dynamics of the q-q interaction make a transition from
the strong (confinement) to the perturbative (QED-like) QCD regime?
• It will occur earliest in the simplest systems
 the pion form factor Fp(Q2) provides our best chance to
determine the relevant distance scale experimentally
applicability of pQCD (GPD’s) to exclusive pion production ?
Access to the DIS Regime @ 12 GeV
with enough luminosity to reach the high-Q2, high-x region!
Counts/hour/
(100 MeV)2 (100 MeV2)
for L=1035 cm-2 sec-1
Extending DIS to High x
The Neutron to Proton
Structure Function Ratio
The Neutron Asymmetry A1
(similar precision for p and d)
Hall C: 3H/3He
CLAS: tagging
spectator proton
12 GeV will access the valence
quark regime (x > 0.3)
3He(e,e’)
Flavor decomposition using SIDIS
Valence quarks
Ee =11 GeV NH3+He3
Flavor decomposition: polarized sea
 Large flavor asymmetry in
unpolarized sea
 Asymmetry in polarized sea?
 First data from HERMES
compatible with zero but have
large uncertainties
 Calculations:
– Instantons (QSM)
(Goeke)
– Pion cloud models ?
More data expected from RHIC SSA in future
Beyond form factors and quark distributions –
Generalized Parton Distributions (GPDs)
X. Ji, D. Mueller, A. Radyushkin (1994-1997)
Proton form
factors, transverse
charge & current
densities
Correlated quark momentum
and helicity distributions in
transverse space - GPDs
Structure functions,
quark longitudinal
momentum & helicity
distributions
Kinematics for deeply excl. experiments
compete with other
experiments
no overlap with other
existing experiments
DVCS:
Single
SpinAsymmetry
Asymmetry
DVCS
Single-Spin
Q2 = 5.4 GeV2
x = 0.35
-t = 0.3 GeV2
CLAS experiment
E0 = 11 GeV
Pe = 80%
L = 1035 cm-2s-1
Run time: 2000 hrs
Many x, Q2 and t values measured simultanously !
Projected precision in extraction of
GPD H at x = x
Projected
results
Spatial Image
orbital angular momentum carried by
quarks : solving the spin puzzle
e
k
g
k'
g*
p
q
q'
p'
At one value of x only
Ingredients:
1) GPD Modeling
2) HERMES 1H(e,e’g)p
(transverse target spin asymmetry)
3) Hall A 2H(e,e’gn)p
Compared to Lattice QCD
For quarks 12 GeV will give final answers
Exclusive 0 production on transverse target
AUT = -
2D (Im(AB*))/p
|A|2(1-x2) - |B|2(x2+t/4m2) - Re(AB*)2x2
0
A ~ 2Hu + Hd
B ~ 2Eu + Ed
+
A ~ Hu - H d
B ~ Eu - Ed
AUT
Asymmetry depends linearly
on the GPD E, which enters
Ji’s sum rule.
0
xB
K. Goeke, M.V. Polyakov,
M. Vanderhaeghen, 2001
Longitudinally polarized Target SSA for p+
Measurement of kT dependent twist-2
distribution provides an independent test of
the Collins fragmentation.
Real part of interference of wave
functions with L=0
and L=1
In noncollinear singlehadron fragmentation
q h
H11(z,k
additional FF H
T()z )
p
kT
quark
Efremov et al.
•Study the PT – dependence of AULsin2f
•Study the possible effect of large unfavored
Collins function.
Transverse Target SSA @11 GeV
CLAS @ 11GeV (NH3)
Collins
p+
AUT ~
p0
pf1T┴, requires final
state interactions +
interference between
different helicity states
Sivers
AUT ~
Simultaneous (with pion SIDIS) measurement of,
exclusive ,+,w with a transversely polarized
target important to control the background.
Transversity in double pion production
The angular distribution of two
hadrons is sensitive to the spin
of the quark
AUT  sin(  R +  S )h1 H
R
1
+ ...
“Collinear” dihadron fragmentation described by
two functions at leading twist:
D1(z,cosqR,Mpp),H1R(z,cosqR,Mpp)
h1
RT
quark
h2
Collins et al,
Ji, Jaffe et al,
Radici et al.
relative transverse momentum of the two hadrons
replaces the PT in single-pion production (No transverse
momentum of the pair center of mass involved )
Dihadron production provides an alternative, “background free” access to transversity
Quark Structure of Nuclei: Origin of the
EMC Effect

Observation that structure functions are altered in nuclei stunned much of the
HEP community 23 years ago

~1000 papers on the topic; BUT more data are needed to uniquely identify the
origin: What alters the quark momentum in the nucleus?
Jlab at 12 GeV
• Precision study of AA
2
D
2
F
F
JLab 12
x
dependence
• Measurements at x>1
• “Polarized EMC effect”
• Flavor-tagged (polarized)
structure functions
• valence vs. sea
contributions
g1(A) – “Polarized EMC Effect”

New calculations indicate larger effect for polarized structure function than for
unpolarized: scalar field modifies lower components of Dirac wave function

Spin-dependent parton distribution functions for nuclei nearly unknown

Can take advantage of modern technology for polarized solid targets to perform
systematic studies – Dynamic Nuclear Polarization
 
g1 A 7 Li
(polarized EMC effect)
g1 p
Curve follows
calculation by
W. Bentz,
I. Cloet,
A. W. Thomas.
“Polarized EMC Effect” – Flavor Tagging

semi-inclusive DIS on polarized targets, measuring p+ and p-, decompose to
extract DuA(x), DdA(x).

Challenging measurement, but have new tools:
– High polarization for a wide variety of targets
– Large acceptance to constrain syst. errors and tune models
Ddv(x)
nuclear matter
DdA(x)
Dd(x)
Ratios
Duv(x)
free nucleon
+ scalar field
+ Fermi
+ vector field
(total)
DuA(x)
Du(x)
x
W. Bentz, I. Cloet, A. W. Thomas
nuclear matter
APV Measurements
APV ~ 8 x 10-5 Q2
E-05-007
0.1 to 100 ppm
• Steady progress in technology
• part per billion systematic
control
• 1% normalization control
• JLab now takes the lead
-New results from HAPPEX
-Photocathodes
-Polarimetry
-Targets
-Diagnostics
-Counting Electronics
DOE Generic Project Timeline
We are here
DOE CD-2 Reviews
September 2007
12 GeV Upgrade: Phases and Schedule
(based on funding guidance provided by DOE-NP in April 2007)
 2004-2005
Conceptual Design (CDR) - finished
 2004-2008
Research and Development (R&D) - ongoing
 2006
Advanced Conceptual Design (ACD) - finished
 2006-2008
Project Engineering & Design (PED) - ongoing
 2009-2013
Construction – starts in ~18 months!
 Accelerator shutdown start mid 2012
 Accelerator commissioning mid 2013
 2013-2015
Pre-Ops (beam commissioning)
 Hall commissioning start late 2013
Summary
The Jlab 12 GeV Upgrade will increase the energy of
CEBAF, provide very high luminosities and will thus
allow to measure with unprecedented precision:
• the high x behaviour of (un)polarised structure functions
• the spin and flavour decomposition in the valence region
• pion and nucleon form factors at high Q2
• single spin asymmetries and kt dependent effects
• deep exclusive processes in multi-differential form
• nuclear effects in (semi)-inclusive scattering
• search for hybrid states
• parity violating asymmetries as a test of the standard model
The ideal laboratory for valence quark physics !
Quantum Numbers of Hybrid Mesons

Quarks
Excited
Flux Tube
S0
+-
L 0
J
PC
J PC  0 - +
like
Hybrid Meson
1
  -+
1
J
PC
1-   ++
1
p, K
Exotic
S 1
J PC
L 0
J PC  1- like
1+   -+
1
J
PC
0 - + 1- + 2 -+
  + - + - +0 1 2
g, 
Flux tube excitation (and parallel quark spins) lead to exotic JPC
Radial
excitations
Mass (GeV)
Meson Map
Each box corresponds
to 4 nonets (2 for L=0)
qq Mesons
2.5
Glueballs
2.0
1.5
2 +–
2 –+
1 ––
1– +
1 +–
1 ++
0 +–
0 –+
0 ++
1.0
L=0
1
2
3
4
(L = qq angular momentum)
Hybrids
2 –+
0 –+
2 ++
exotic
nonets
Lattice
1-+ 1.9 GeV
2+- 2.1 GeV
0+- 2.3 GeV
Unraveling the Quark WNC Couplings
V
A
A
C2i  2gVe gAi
V
C1i  2gAe gVi

12 GeV:
(2C2u-C2d)=0.01
PDG: -0.08 ± 0.24
Theory: +0.0986
Vector quark couplings
Axial-vector quark couplings